The effect of maternal photoperiod on seasonal dormancy in Arabidopsis thaliana (Brassicaceae)

The maternal photoperiod at the time of seed maturation can predict the seasonal conditions of newly dispersed seeds. We investigated the effects of maternal photoperiod on seasonal dormancy in Arabidopsis thaliana using a set of F6 recombinant inbred lines derived from a cross between individuals from two natural populations (CaI-0 and Tac-0) differing in cold requirements for germination. We grew 40 Cal X Tac lines in a long-day photoperiod (8 h of full spectrum light plus 8 h of low-fluence incandescent light) and a shortday photoperiod (8 h full spectrum light). We then exposed seeds from each family and maternal photoperiod to either a cold stratification treatment (4 degreesC, 21 d) or no cold stratification. Both maternal photoperiod and progeny stratification influenced the percentage of seeds that germinated and the speed of germination. The short-day photoperiod caused increased responsiveness to stratification, with higher germination percentages and speeds in stratified seeds. Stratification influenced the expression of maternal photoperiod effects, such that short days increased germination percentage and speed in stratified seeds but inhibited germination in unstratified seeds. Families differed significantly in their plasticity to maternal photoperiod and stratification, but genetic variation for plasticity to maternal photoperiod was expressed only in unstratified seeds. Because the expression of maternal photoperiod effects and genetic variation for photoperiod effects depended on progency stratification, the evolution of these maternal effects will depend on the seasonal environment experienced by progeny.